Is Reality Really Real? — An Introduction to Bell’s Inequalities

Alessio Avella, Marco Genovese

Muhammad Suhail Zubairy

Abstract The first round of the Einstein–Bohr debates took place when Einstein challenged Bohr’s principle of complementarity at the Solvay conference in 1927 and Bohr successfully defended it. The most serious challenge, however, came in 1935 through a paper by Einstein, Podolsky, and Rosen (EPR) when they argued about the incompleteness of quantum mechanics through a gedanken experiment motivating an approach based on hidden variables. In this chapter, the EPR argument about the incompleteness of quantum mechanics and Bohr’s reply to it, are presented. The ultimate answer came almost 30 years later, almost ten years after Einstein’s death, and the answer was nothing what Einstein would have expected. Bell’s inequality and the subsequent Bell–CHSH inequality, that are satisfied by all theories based on the “self-evident truths” of reality and locality are discussed. The startling result that quantum mechanics violates Bell’s inequality and that the experimental results are in agreement with the prediction of quantum mechanics is presented.

Afshin Shafiee, Mehdi Golshani

In the experimental verification of Bell’s inequalities in real photonic experiments, it is generally believed that the so-called fair sampling assumption (which means that a small fraction of results provide a fair statistical sample) has an unavoidable role. Here, we want to show that the interpretation of these experiments is really independent of the fair sampling assumption. For this purpose, we derive a more efficient Bell-type inequality which is a CHSH-type inequality in real experiments, using some alternative assumptions. Furthermore, Quantum mechanics violates our proposed inequality, In his celebrated 1964 paper, John Bell considered a system consisting of two spin-1 particles in a singlet state [1]. He showed that the correlation 2 between the results of two experiments done on such spatially separated particles

Louis Sica

M. S. Guimarães, I. Roditi, Silvio Paolo sorella

A concise and self-contained introduction to the Bell inequality in relativistic Quantum Field Theory is presented. Taking the example of a real scalar massive field, the violation of the Bell inequality in the vacuum state and for causal complementary wedges is illustrated.